Combine metrics into graphs on either part of the name

[sciurus]

I'd like to be able to configure how metrics are combined in graphs. Right now, they're always combined based on the left half of the metric name (e.g. cpu-0). I'd like to be able to choose combining based on the right half (e.g. cpu-system) instead. For example, let's say in the profile builder I select the metrics cpu-0/cpu-system, cpu-0/cpu-user, cpu-1/cpu-system, and cpu-1/cpu-user. Before finishing the builder, I would like to be able to select between

1. A graph that combines cpu-0/cpu-system and cpu-0/cpu-user followed by a graph that combines cpu-1/cpu-system and cpu-1/cpu-user.
2. A graph that combines cpu-0/cpu-system and cpu-1/cpu-system followed by a graph that combines cpu-0/cpu-user and cpu-1/cpu-user.

This is similar to but simpler than Issue 57.

[jessereynolds]

+1

[xor-gate]

This would still be very usefull :+1: